Date: Wed, 2 Jul 2014 19:34:20 +0300
From: Gleb Natapov <gleb@kernel.org>
To: Tang Chen <tangchen@cn.fujitsu.com>
Cc: mtosatti@redhat.com, kvm@vger.kernel.org, laijs@cn.fujitsu.com,
        isimatu.yasuaki@jp.fujitsu.com, guz.fnst@cn.fujitsu.com,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/4] kvm, memory-hotplug: Update ept identity pagetable
 when it is migrated.
Message-ID: <20140702163420.GC4399@minantech.com>
References: <1404291637-15048-1-git-send-email-tangchen@cn.fujitsu.com>
 <1404291637-15048-4-git-send-email-tangchen@cn.fujitsu.com>
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On Wed, Jul 02, 2014 at 05:00:36PM +0800, Tang Chen wrote:
> ept identity pagetable is pinned in memory, and as a result it cannot be
> migrated/hot-removed.
> 
> But actually it doesn't need to be pinned in memory.
> 
> This patch introduces a new vcpu request: KVM_REQ_MIGRATE_EPT to reset ept
> indetity pagetable related variable. This request will be made when
> kvm_mmu_notifier_invalidate_page() is called when the page is unmapped
> from the qemu user space to reset kvm->arch.ept_identity_pagetable to NULL.
> And will also be made when ept violation happens to reset
> kvm->arch.ept_identity_pagetable to the new page.

kvm->arch.ept_identity_pagetable is never used as a page address, just
boolean null/!null to see if identity pagetable is initialized. I do
not see why would we want to track its address at all. Changing it to bool
and assigning true during initialization should be enough.


--
			Gleb.
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